Alright let's see here:
Movement one: Solid opening. The theme is introduced well, and the horn entrance is constructed perfectly. Your sonata form is not as skewed, too. Well-structured to say the least here. I like the minor section, and the piano right hand. But your left hand could really use some work. It mostly causes the whole piece's harmonic structure to run dry. What I mean is, if you thickened up yoru piano writing, it would not only sound fuller, but it would flow more, and make it sound less..."amateurish" for lack of a better word. Ok, also, the piano isn't a violin. You have it play a lot of notes in a row. This also takes away from some of the better aspects of your piece. Perhaps do them in alternating octaves instead? The nice little mini cadenza is cool, although kind of boring. Nice trill haha, you saved it there. You need to show off the horn more...you have it doing like all quarter and eighth notes...have it do some arpeggios!! When the piano comes back in, its as solid as the horn entrance, which is good, and you end this movement well.
Movement two: It's nice. Your piano left hand is a little more interesting, and it kind of feels like a starry night. Definately one of the prettier things in the piece. harmonically thin, still, though.
Movement three: Fun! The best movement by far. Your counterpoint is naturally good in feel. Your harmony is again fuller, but sometimes orchestrated incorrectly or awkwardly. For example, in the beginning, your piano jumps an octave to a Major 2nd chord, which sounds kind of out of place, and oddly dissonant even though it fits the chord. If you lower it an octave or two, perhaps conceal it with other parts of the chord, it'll sound good. The horn isn't used much in this movement, but when it is, it kind of seems like an add-on instead of the star of the show. I realize this isn't a concerto, but this movement needs more horn! The dialogue just isn't there. Your chordal structure is the best in this movement, as I think I said before. Your harmony filled out, and the piano sounds more like it should. You do this especially well in 2:20-2:40. You also ended this movement well...definately the best of the three.
Getting better! My only SOLE complaint is: you use a grand total of 2 chords: I and V. Thats it. 2. E-flat and B-flat. That makes for EXTREMELY amateurish and boring music. However, you managed to spice it up well enough.
I think this can stay as a Major Work.
Good job!
Nico